Digenic Leigh syndrome on the background of the m.11778G>A Leber hereditary optic neuropathy variant.

Leigh syndrome spectrum (LSS) is a primary mitochondrial disorder defined neuropathologically by a subacute necrotizing encephalomyelopathy and characterized by bilateral basal ganglia and/or brainstem lesions. LSS is associated with variants in several mitochondrial DNA genes and more than 100 nuclear genes, most often related to mitochondrial complex I (CI) dysfunction. Rarely, LSS has been reported in association with primary Leber hereditary optic neuropathy (LHON) variants of the mitochondrial DNA, coding for CI subunits (m.3460G>A in MT-ND1, m.11778G>A in MT-ND4 and m.14484T>C in MT-ND6). The underlying mechanism by which these variants manifest as LSS, a severe neurodegenerative disease, as opposed to the LHON phenotype of isolated optic neuropathy, remains an open question. Here, we analyse the exome sequencing of six probands with LSS carrying primary LHON variants, and report digenic co-occurrence of the m.11778G > A variant with damaging heterozygous variants in nuclear disease genes encoding CI subunits as a plausible explanation. Our findings suggest a digenic mechanism of disease for m.11778G>A-associated LSS, consistent with recent reports of digenic disease in individuals manifesting with LSS due to biallelic variants in the recessive LHON-associated disease gene DNAJC30 in combination with heterozygous variants in CI subunits.

Age-dependent retinal neuroaxonal degeneration in children and adolescents with Leber hereditary optic neuropathy under idebenone therapy.

BACKGROUND: The aim of this study was to investigate the neuroretinal structure of young patients with Leber hereditary optic neuropathy (LHON). METHODS: For this retrospective cross-sectional analysis, the peripapillary retinal nerve fiber layer (pRNFL) thickness and the macular retinal layer volumes were measured by optical coherence tomography. Patients aged 12 years or younger at disease onset were assigned to the childhood-onset (ChO) group and those aged 13-16 years to the early teenage-onset (eTO) group. All patients received treatment with idebenone. The same measurements were repeated in age-matched control groups with healthy subjects. RESULTS: The ChO group included 11 patients (21 eyes) and the eTO group 14 patients (27 eyes). Mean age at onset was 8.6 ± 2.7 years in the ChO group and 14.8 ± 1.0 years in the eTO group. Mean best-corrected visual acuity was 0.65 ± 0.52 logMAR in the ChO group and 1.60 ± 0. 51 logMAR in the eTO group (p < 0.001). Reduced pRNFL was evident in the eTO group compared to the ChO group (46.0 ± 12.7 µm vs. 56.0 ± 14.5 µm, p = 0.015). Additionally, a significantly lower combined ganglion cell and inner plexiform layer volume was found in the eTO compared to the ChO group (0.266 ± 0.0027 mm3 vs. 0.294 ± 0.033 mm3 , p = 0.003). No difference in these parameters was evident between the age-matched control groups. CONCLUSION: Less neuroaxonal tissue degeneration was observed in ChO LHON than in eTO LHON, a finding that may explain the better functional outcome of ChO LHON.

DNAJC30 defect: a frequent cause of recessive Leber hereditary optic neuropathy and Leigh syndrome.

The recent description of biallelic DNAJC30 variants in Leber hereditary optic neuropathy (LHON) and Leigh syndrome challenged the longstanding assumption for LHON to be exclusively maternally inherited and broadened the genetic spectrum of Leigh syndrome, the most frequent paediatric mitochondrial disease. Herein, we characterize 28 so far unreported individuals from 26 families carrying a homozygous DNAJC30 p.Tyr51Cys founder variant, 24 manifesting with LHON, two manifesting with Leigh syndrome, and two remaining asymptomatic. This collection of unreported variant carriers confirms sex-dependent incomplete penetrance of the homozygous variant given a significant male predominance of disease and the report of asymptomatic homozygous variant carriers. The autosomal recessive LHON patients demonstrate an earlier age of disease onset and a higher rate of idebenone-treated and spontaneous recovery of vision in comparison to reported figures for maternally inherited disease. Moreover, the report of two additional patients with childhood- or adult-onset Leigh syndrome further evidences the association of DNAJC30 with Leigh syndrome, previously only reported in a single childhood-onset case.

Real-World Clinical Experience With Idebenone in the Treatment of Leber Hereditary Optic Neuropathy.

BACKGROUND: Leber hereditary optic neuropathy (LHON) leads to bilateral central vision loss. In a clinical trial setting, idebenone has been shown to be safe and to provide a trend toward improved visual acuity, but long-term evidence of effectiveness in real-world clinical practice is sparse. METHODS: Open-label, multicenter, retrospective, noncontrolled analysis of long-term visual acuity and safety in 111 LHON patients treated with idebenone (900 mg/day) in an expanded access program. Eligible patients had a confirmed mitochondrial DNA mutation and had experienced the onset of symptoms (most recent eye) within 1 year before enrollment. Data on visual acuity and adverse events were collected as per normal clinical practice. Efficacy was assessed as the proportion of patients with either a clinically relevant recovery (CRR) or a clinically relevant stabilization (CRS) of visual acuity. In the case of CRR, time to and magnitude of recovery over the course of time were also assessed. RESULTS: At time of analysis, 87 patients had provided longitudinal efficacy data. Average treatment duration was 25.6 months. CRR was observed in 46.0% of patients. Analysis of treatment effect by duration showed that the proportion of patients with recovery and the magnitude of recovery increased with treatment duration. Average gain in best-corrected visual acuity for responders was 0.72 logarithm of the minimal angle of resolution (logMAR), equivalent to more than 7 lines on the Early Treatment Diabetic Retinopathy Study (ETDRS) chart. Furthermore, 50% of patients who had a visual acuity below 1.0 logMAR in at least one eye at initiation of treatment successfully maintained their vision below this threshold by last observation. Idebenone was well tolerated, with most adverse events classified as minor. CONCLUSIONS: These data demonstrate the benefit of idebenone treatment in recovering lost vision and maintaining good residual vision in a real-world setting. Together, these findings indicate that idebenone treatment should be initiated early and be maintained more than 24 months to maximize efficacy. Safety results were consistent with the known safety profile of idebenone.

MRPL44 mutations cause a slowly progressive multisystem disease with childhood-onset hypertrophic cardiomyopathy.

Defects in mitochondrial translation may lead to combined respiratory chain deficiency and typically cause childhood-onset multisystem disease. Only recently, a homozygous missense mutation (c.467T > G, p.Leu156Arg) in MRPL44, encoding a protein of the large subunit of the mitochondrial ribosome, has been identified in two siblings with hypertrophic cardiomyopathy. Using exome sequencing, we identified two further unrelated patients harboring the previously reported mutation c.467T > G, p.Leu156Arg in MRPL44 in the homozygous state and compound heterozygous with a novel missense mutation c.233G > A, p.Arg78Gln, respectively. Both patients presented with childhood-onset hypertrophic cardiomyopathy, which seems to be the core clinical feature associated with MRPL44 deficiency. However, we observed several additional clinical signs and symptoms including pigmentary retinopathy, hemiplegic migraine, Leigh-like lesions on brain MRI, renal insufficiency, and hepatopathy. Our findings expand the clinical spectrum associated with MRPL44 mutations and indicate that MRPL44-associated mitochondrial dysfunction can also manifest as a progressive multisystem disease with central nervous system involvement. Of note, neurological and neuro-ophthalmological impairment seems to be a disease feature of the second and third decades of life, which should be taken into account in patient management and counseling.

Exonic microdeletions of the gephyrin gene impair GABAergic synaptic inhibition in patients with idiopathic generalized epilepsy.

Gephyrin is a postsynaptic scaffolding protein, essential for the clustering of glycine and γ-aminobutyric acid type-A receptors (GABAARs) at inhibitory synapses. An impairment of GABAergic synaptic inhibition represents a key pathway of epileptogenesis. Recently, exonic microdeletions in the gephyrin (GPHN) gene have been associated with neurodevelopmental disorders including autism spectrum disorder, schizophrenia and epileptic seizures. Here we report the identification of novel exonic GPHN microdeletions in two patients with idiopathic generalized epilepsy (IGE), representing the most common group of genetically determined epilepsies. The identified GPHN microdeletions involve exons 5-9 (Δ5-9) and 2-3 (Δ2-3), both affecting the gephyrin G-domain. Molecular characterization of the GPHN Δ5-9 variant demonstrated that it perturbs the clustering of regular gephyrin at inhibitory synapses in cultured mouse hippocampal neurons in a dominant-negative manner, resulting in a significant loss of γ2-subunit containing GABAARs. GPHN Δ2-3 causes a frameshift resulting in a premature stop codon (p.V22Gfs*7) leading to haplo-insufficiency of the gene. Our results demonstrate that structural exonic microdeletions affecting the GPHN gene constitute a rare genetic risk factor for IGE and other neuropsychiatric disorders by an impairment of the GABAergic inhibitory synaptic transmission.

The lifelong course of chronic epilepsy: the Chalfont experience.

The long-term outcome of chronic epilepsy remains largely unknown, despite a long historical experience. We report the lifelong course of epilepsy of an historical cohort of 235 subjects who were in residential care at the Chalfont Centre for Epilepsy: 122 had comprehensive post-mortem examination. The populations admitted as resident to the centre over time followed the evolution of society's perception of epilepsy. 'Early residents' (before 1972) were admitted for sheltered employment, escaping stigmatization, whereas 'later' residents with more severe epilepsies were admitted for care. Subjects admitted before 1972 were similar to subjects followed nowadays as outpatients, whereas patients admitted later with a higher burden of disabilities are often those in residential care. This long follow-up allowed exploration of a wide spectrum of epilepsies, affecting both subjects who were otherwise healthy and those with co-morbidities. Age at death showed a bimodal distribution with an early peak of mortality between 45-50 years old, whilst the remainder had life expectancy comparable to the general population. As a group, subjects who had post-mortem examination were not significantly different from patients who did not have post-mortem examination, but post-mortem examination provided data that were otherwise unavailable. For those who had post-mortem examination, sudden unexpected death in epilepsy (SUDEP, 18% of all deaths) did not fully explain the early mortality, to which co-morbidities contributed. High seizure frequency was a significant independent predictor of early death even after excluding SUDEP (e.g. reduction in years of life for those who had >4 seizures/month compared with those who had <1 seizure/month: 13 years; 95% confidence interval: 6-19; overall P = 0.0006). Those who survived to older age increasingly went into spontaneous remission lasting until death (in the whole cohort, 38/166, 23% of those who died in or after sixth decade). In subjects who had post-mortem examination, older age (odds ratio = 1.13; 95% confidence interval: 1.06-1.20) and presence of neuropathologically confirmed degenerative changes (that were not the cause of epilepsy) (odds ratio 7.14; 1.95-26.2) were independent predictors of terminal remission. Epilepsy may cause premature death indirectly through co-morbid conditions. Terminal remission occurs even without prior remissions; ageing may improve epilepsy drug responsiveness although unknown factors related to the natural history may also play a role.

Epilepsy, hippocampal sclerosis and febrile seizures linked by common genetic variation around SCN1A.

Epilepsy comprises several syndromes, amongst the most common being mesial temporal lobe epilepsy with hippocampal sclerosis. Seizures in mesial temporal lobe epilepsy with hippocampal sclerosis are typically drug-resistant, and mesial temporal lobe epilepsy with hippocampal sclerosis is frequently associated with important co-morbidities, mandating the search for better understanding and treatment. The cause of mesial temporal lobe epilepsy with hippocampal sclerosis is unknown, but there is an association with childhood febrile seizures. Several rarer epilepsies featuring febrile seizures are caused by mutations in SCN1A, which encodes a brain-expressed sodium channel subunit targeted by many anti-epileptic drugs. We undertook a genome-wide association study in 1018 people with mesial temporal lobe epilepsy with hippocampal sclerosis and 7552 control subjects, with validation in an independent sample set comprising 959 people with mesial temporal lobe epilepsy with hippocampal sclerosis and 3591 control subjects. To dissect out variants related to a history of febrile seizures, we tested cases with mesial temporal lobe epilepsy with hippocampal sclerosis with (overall n = 757) and without (overall n = 803) a history of febrile seizures. Meta-analysis revealed a genome-wide significant association for mesial temporal lobe epilepsy with hippocampal sclerosis with febrile seizures at the sodium channel gene cluster on chromosome 2q24.3 [rs7587026, within an intron of the SCN1A gene, P = 3.36 × 10(-9), odds ratio (A) = 1.42, 95% confidence interval: 1.26-1.59]. In a cohort of 172 individuals with febrile seizures, who did not develop epilepsy during prospective follow-up to age 13 years, and 6456 controls, no association was found for rs7587026 and febrile seizures. These findings suggest SCN1A involvement in a common epilepsy syndrome, give new direction to biological understanding of mesial temporal lobe epilepsy with hippocampal sclerosis with febrile seizures, and open avenues for investigation of prognostic factors and possible prevention of epilepsy in some children with febrile seizures.

Genetic variants affecting NQO1 protein levels impact the efficacy of idebenone treatment in Leber hereditary optic neuropathy.

Idebenone, the only approved treatment for Leber hereditary optic neuropathy (LHON), promotes recovery of visual function in up to 50% of patients, but we can neither predict nor understand the non-responders. Idebenone is reduced by the cytosolic NAD(P)H oxidoreductase I (NQO1) and directly shuttles electrons to respiratory complex III, bypassing complex I affected in LHON. We show here that two polymorphic variants drastically reduce NQO1 protein levels when homozygous or compound heterozygous. This hampers idebenone reduction. In its oxidized form, idebenone inhibits complex I, decreasing respiratory function in cells. By retrospectively analyzing a large cohort of idebenone-treated LHON patients, classified by their response to therapy, we show that patients with homozygous or compound heterozygous NQO1 variants have the poorest therapy response, particularly if carrying the m.3460G>A/MT-ND1 LHON mutation. These results suggest consideration of patient NQO1 genotype and mitochondrial DNA mutation in the context of idebenone therapy.

Rare deletions at 16p13.11 predispose to a diverse spectrum of sporadic epilepsy syndromes.

Deletions at 16p13.11 are associated with schizophrenia, mental retardation, and most recently idiopathic generalized epilepsy. To evaluate the role of 16p13.11 deletions, as well as other structural variation, in epilepsy disorders, we used genome-wide screens to identify copy number variation in 3812 patients with a diverse spectrum of epilepsy syndromes and in 1299 neurologically-normal controls. Large deletions (> 100 kb) at 16p13.11 were observed in 23 patients, whereas no control had a deletion greater than 16 kb. Patients, even those with identically sized 16p13.11 deletions, presented with highly variable epilepsy phenotypes. For a subset of patients with a 16p13.11 deletion, we show a consistent reduction of expression for included genes, suggesting that haploinsufficiency might contribute to pathogenicity. We also investigated another possible mechanism of pathogenicity by using hybridization-based capture and next-generation sequencing of the homologous chromosome for ten 16p13.11-deletion patients to look for unmasked recessive mutations. Follow-up genotyping of suggestive polymorphisms failed to identify any convincing recessive-acting mutations in the homologous interval corresponding to the deletion. The observation that two of the 16p13.11 deletions were larger than 2 Mb in size led us to screen for other large deletions. We found 12 additional genomic regions harboring deletions > 2 Mb in epilepsy patients, and none in controls. Additional evaluation is needed to characterize the role of these exceedingly large, non-locus-specific deletions in epilepsy. Collectively, these data implicate 16p13.11 and possibly other large deletions as risk factors for a wide range of epilepsy disorders, and they appear to point toward haploinsufficiency as a contributor to the pathogenicity of deletions.

Neuropathology of the blood-brain barrier and pharmaco-resistance in human epilepsy.

Blood-brain barrier dysfunction is implicated in various neurological conditions. Modulating the blood-brain barrier may have therapeutic value. Progress is hindered by our limited understanding of the pathophysiology of the blood-brain barrier in humans, partly due to restricted availability of human tissue, and because human tissue can only provide limited data about temporal patterns of change. We addressed these important challenges by examining surgically resected brain tissue with various lengths of interval between intracranial depth electrode-related injury and resection, and post-mortem whole brain from patients with drug-sensitive or drug-resistant chronic epilepsy and controls. In this valuable set of resources, we found that: (i) there is a highly localized overexpression of P-glycoprotein in the epileptogenic hippocampus of patients with drug-resistant epilepsy; (ii) this overexpression appears specific to P-glycoprotein and does not affect other transporters; (iii) P-glycoprotein is expressed on the vascular endothelium and end-feet of vascular glia (forming a 'double cuff') in drug-resistant epileptic cases but not in post-mortem controls or surgical epilepsy tissue with electrode-related injuries; (iv) an acute insult from intracranial electrode recording causes localized inflammation, increased blood-brain barrier permeability and structural changes to vasculature detectable for up to at least 330 days and (v) chronic epilepsy is associated with inflammation, enhanced blood-brain barrier permeability and increased P-glycoprotein expression. The occurrence of seizures appears central to P-glycoprotein overexpression. Our findings have potential clinical impact because they directly improve our understanding of blood-brain barrier disruption and transporter expression in humans. In particular, our findings show that the expression of P-glycoprotein in humans is compatible with the inherent assumptions of one current hypothesis of multidrug resistance, and that the specific upregulation of P-glycoprotein expression is likely to be associated with ongoing chronic seizures. There may be a therapeutic window after initial acute injury for the prevention of P-glycoprotein overexpression, and thus this one potential component of drug resistance. Our findings add to the need for careful consideration of the benefit and risks of invasive electroencephalographic recording in surgical evaluation of drug-resistant epilepsy.

Childhood versus early-teenage onset Leber's hereditary optic neuropathy: visual prognosis and capacity for recovery.

OBJECTIVE: In Leber's hereditary optic neuropathy (LHON) in children and teenagers, the influence of age on visual prognosis has not yet been investigated. METHODS: Patients from the mitoNET registry with LHON onset at age 4-16 years with at least 4 years of follow-up without treatment were included. Visual acuity (VA) at baseline, lowest VA ever recorded (nadir) and VA at end of follow-up were compared between childhood onset (ChO, ≤12 years of age) and early-teenage onset (eTO; 13-16 years). RESULTS: Out of 231 patients with LHON, 19 met the inclusion criteria (8.2%). There were 11 patients in the ChO and 8 patients in the eTO group. Mean age at onset was 8.6 (SD 2.1) years (ChO) and 15.4 (SD 0.7) years (eTO) (p<0.00001). Follow-up was mean 184 (SD 129) months (ChO) and 119 (SD 78) months (eTO) (p=0.22). Baseline VA was similar between both groups in better (p=0.96) and worse eyes (p=0.54). In worse eyes, both groups deteriorated similarly (p=0.79) until nadir and showed similar recovery until end of follow-up (p=0.38). In better eyes, both groups deteriorated similarly (p=0.16) until nadir. From nadir until end of follow-up, better eyes in the ChO group showed a significantly better recovery (-0.35 (SD 0.36) vs -0.01 (SD 0.06) logMAR; p=0.02) than eTO eyes. CONCLUSION: Visual prognosis of LHON in children is much more favourable in cases of childhood onset (≤12 years of age) as compared with teenage onset (13-16 years), mostly due to better recovery from nadir in childhood onset.

Investigation of hypoxia-inducible factor-1α in hippocampal sclerosis: a postmortem study.

PURPOSE: Hypoxia-inducible factor-1α (HIF-1α) is involved in critical aspects of cell survival in response to hypoxia and regulates vascular endothelial growth factor (VEGF) expression. Previous experimental and human studies in epilepsy show up-regulation of VEGF following seizures, although expression of HIF-1α as its potential regulator has not been explored. We used a postmortem (PM) series from patients with epilepsy and hippocampal sclerosis (HS) to investigate patterns of expression of HIF-1α and VEGF and their potential contribution to neuroprotection. METHOD: In 33 PMs (17 cases with unilateral HS, 3 with bilateral HS, 3 with No-HS, and 10 controls), we quantified neuronal immunolabeling for HIF-1α and VEGF in hippocampal subfields. KEY FINDINGS: HIF-1α- and VEGF-immunopositive hippocampal neurones were observed in HS, No-HS, and also in control cases; there was no significant difference in overall labeling between epilepsy cases and controls. In positive cases, HIF-1α and VEGF neuronal labeling localized primarily in CA1, CA4, and CA3 subfields in all groups; significantly more positive neurons were seen in the entorhinal cortex in epilepsy cases (p < 0.05). Labeling lateralized to the side of sclerosis in unilateral HS cases, with significant differences between hemispheres (p < 0.05). There was a trend for high HIF-1α labeling scores in patients with Dravet syndrome without HS and sudden unexpected death in epilepsy (SUDEP) cases, and lower scores with long seizure-free periods prior to death. Hippocampal HIF-1α and VEGF labeling showed a significant correlation. There was neuronal colocalization of HIF-1α and VEGF. SIGNIFICANCE: Regional expression patterns are in keeping with seizure-related activation of HIF-1α and VEGF. The prominent expression in non-HS cases could support an overall neuroprotective effect. Correlation between HIF-1α and VEGF neuronal immunolabeling supports HIF-1α-mediated induction of VEGF in epilepsy.

Neurofibrillary tangle pathology and Braak staging in chronic epilepsy in relation to traumatic brain injury and hippocampal sclerosis: a post-mortem study.

The long-term pathological effects of chronic epilepsy on normal brain ageing are unknown. Previous clinical and epidemiological studies show progressive cognitive decline in subsets of patients and an increased prevalence of Alzheimer's disease in epilepsy. In a post-mortem series of 138 patients with long-term, mainly drug-resistant epilepsy, we carried out Braak staging for Alzheimer's disease neurofibrillary pathology using tau protein immunohistochemistry. The stages were compared with clinicopathological factors, including seizure history and presence of old traumatic brain injury. Overall, 31% of cases were Braak Stage 0, 36% Stage I/II, 31% Stage III/IV and 2% Stage V/VI. The mean age at death was 56.5 years and correlated with Braak stage (P < 0.001). Analysis of Braak stages within age groups showed a significant increase in mid-Braak stages (III/IV), in middle age (40-65 years) compared with data from an ageing non-epilepsy series (P < 0.01). There was no clear relationship between seizure type (generalized or complex partial), seizure frequency, age of onset and duration of epilepsy with Braak stage although higher Braak stages were noted with focal more than with generalized epilepsy syndromes (P < 0.01). In 30% of patients, there was pathological evidence of traumatic brain injury that was significantly associated with higher Braak stages (P < 0.001). Cerebrovascular disease present in 40.3% and cortical malformations in 11.3% were not significantly associated with Braak stage. Astrocytic-tau protein correlated with the presence of both traumatic brain injury (P < 0.01) and high Braak stage (P < 0.001). Hippocampal sclerosis, identified in 40% (bilateral in 48%), was not associated with higher Braak stages, but asymmetrical patterns of tau protein accumulation within the sclerotic hippocampus were noted. In over half of patients with cognitive decline, the Braak stage was low indicating causes other than Alzheimer's disease pathology. In summary, there is evidence of accelerated brain ageing in severe chronic epilepsy although progression to high Braak stages was infrequent. Traumatic brain injury, but not seizures, was associated with tau protein accumulation in this series. It is likely that Alzheimer's disease pathology is not the sole explanation for cognitive decline associated with epilepsy.

Dravet syndrome as epileptic encephalopathy: evidence from long-term course and neuropathology.

Dravet syndrome is an epilepsy syndrome of infantile onset, frequently caused by SCN1A mutations or deletions. Its prevalence, long-term evolution in adults and neuropathology are not well known. We identified a series of 22 adult patients, including three adult post-mortem cases with Dravet syndrome. For all patients, we reviewed the clinical history, seizure types and frequency, antiepileptic drugs, cognitive, social and functional outcome and results of investigations. A systematic neuropathology study was performed, with post-mortem material from three adult cases with Dravet syndrome, in comparison with controls and a range of relevant paediatric tissue. Twenty-two adults with Dravet syndrome, 10 female, were included, median age 39 years (range 20-66). SCN1A structural variation was found in 60% of the adult Dravet patients tested, including one post-mortem case with DNA extracted from brain tissue. Novel mutations were described for 11 adult patients; one patient had three SCN1A mutations. Features of Dravet syndrome in adulthood include multiple seizure types despite polytherapy, and age-dependent evolution in seizure semiology and electroencephalographic pattern. Fever sensitivity persisted through adulthood in 11 cases. Neurological decline occurred in adulthood with cognitive and motor deterioration. Dysphagia may develop in or after the fourth decade of life, leading to significant morbidity, or death. The correct diagnosis at an older age made an impact at several levels. Treatment changes improved seizure control even after years of drug resistance in all three cases with sufficient follow-up after drug changes were instituted; better control led to significant improvement in cognitive performance and quality of life in adulthood in two cases. There was no histopathological hallmark feature of Dravet syndrome in this series. Strikingly, there was remarkable preservation of neurons and interneurons in the neocortex and hippocampi of Dravet adult post-mortem cases. Our study provides evidence that Dravet syndrome is at least in part an epileptic encephalopathy.

Vitamin B12 in Leber hereditary optic neuropathy mutation carriers: a prospective cohort study.

BACKGROUND: Leber hereditary optic neuropathy (LHON) is the most common mitochondrial disorder, frequently resulting in acute or subacute severe bilateral central vision loss. Vitamin B12 deficiency is also a known cause of optic neuropathy through mitochondrial dysfunction. Here we evaluated the prevalence and clinical significance of vitamin B12 deficiency in a large cohort of LHON patients and asymptomatic mutation carriers from a tertiary referral center. METHODS: From the Munich LHON prospective cohort study, participants included all LHON patients and asymptomatic LHON mutation carriers, who were recruited between February 2014 and March 2020 and consented to participate. Neurological, general, and ophthalmological examinations were regularly performed, as were laboratory tests. Vitamin B12 deficiency was diagnosed if serum vitamin B12 was below 201 pg/mL, or if 201-339 pg/mL plus low serum holotranscobalamin or elevated serum methylmalonic acid or elevated total plasma homocysteine. RESULTS: We analyzed 244 subjects, including 147 symptomatic LHON patients (74% males) and 97 asymptomatic mutation carriers (31% males). Median age at study baseline was 34 years (range 5-82 years). The prevalence of vitamin B12 deficiency was higher for LHON mutation carriers than for the general population in all age categories. This was statistically significant for the LHON mutation carriers under 65 years (21% vs. 5-7%, p = 0.002). While vitamin B12 deficiency prevalence was not statistically different between LHON patients and asymptomatic mutation carriers, its clinical correlates, e.g., macrocytosis and polyneuropathy, were more frequent in the subgroup of LHON patients. Excessive alcohol consumption was a significant predictor of vitamin B12 deficiency (p < 0.05). CONCLUSIONS: The high prevalence of vitamin B12 deficiency in LHON mutation carriers, both asymptomatic mutation carriers and LHON patients, highlights the need for regular vitamin B12 screening in this population, in order to ensure early treatment, aiming for better outcomes. Our study is not conclusive regarding vitamin B12 deficiency as determinant for disease conversion in LHON, and further research is warranted to disentangle the role of vitamin B12 in the pathophysiology and prognosis of LHON.

Neuroimaging and neuropathology of Dravet syndrome.

Brain magnetic resonance imaging (MRI) studies in patients with Dravet syndrome and SCN1A mutations have shown abnormal findings in a small minority of patients. The origin of the structural abnormalities--such focal brain atrophy, cortical dysplasia, and hippocampal sclerosis--observed in some children remains unclear. There seems to be no correlation between the presence of MRI abnormalities and duration of epilepsy, age at seizure onset, or the frequency of episodes of status epilepticus having occurred early in life. Recent descriptions of Rasmussen syndrome and of the hemiconvulsion-hemiplegia syndrome in isolated patients with SCN1A mutations are of uncertain meaning but might indicate that co-occurring immunomediated or seizure-induced structural changes can, in turn, become a substrate for the severe epileptic encephalopathy. The few available neuropathologic studies of Dravet syndrome have provided inconsistent findings, including evidence of subtle brain malformation. However, the underlying dysfunction of the SCN1A gene might confer to the brain a unique profile of vulnerability whose consequences are not easily disclosed by neuropathology and require specific experimental settings to be fully appreciated. There would seem to be value in studies in animal models of these aspects, as well as prospective studies in humans, with a particular view to establishing if earlier diagnosis and efforts at seizure control may influence the development of any clinical, imaging, or pathologic deterioration.

Investigation of widespread neocortical pathology associated with hippocampal sclerosis in epilepsy: a postmortem study.

PURPOSE: One possible cause for surgical failure following temporal lobectomy for the treatment of epilepsy due to classical hippocampal sclerosis (CHS) is the presence of more widespread cortical changes. Neocortical changes in CHS shown by quantitative neuroimaging studies may involve hippocampal projection pathways. Our aim was to quantitate neocortical pathology using a postmortem series of brains from patients with epilepsy and CHS. METHODS: Sections from 13 cortical regions from both left and right hemispheres, including hippocampal projection pathways, were examined from nine epilepsy patients with unilateral CHS (4), bilateral CHS (2), non-CHS (3), and non-epilepsy controls (4). Using GFAP, CD68, and NPY immunohistochemistry as markers of acquired neocortical pathology, quantitative analysis of the staining fractions in the cortex and white matter was carried out. KEY FINDINGS: Higher staining fractions were observed for all markers in both cortex and white matter in CHS patients, which was significantly different for CD68 and NPY compared to controls (p < 0.05) but not to non-CHS epilepsy cases. There was no significant difference between staining fractions in left and right hemispheres for unilateral CHS cases. Regional analysis showed preferential gliosis and microgliosis of temporal poles, frontal poles, and orbitofrontal cortex in epilepsy cases. SIGNIFICANCE: This study supports acquired neocortical pathology in epilepsy patients both with and without CHS. Cortical pathology does not show lateralization to the side of CHS. Preferential involvement of the temporal and frontal poles may relate to other factors, such as cortical injury associated with seizures, rather than involvement through hippocampal pathways.

Genomic microdeletions associated with epilepsy: not a contraindication to resective surgery.

PURPOSE: Several recent reports of genomic microdeletions in epilepsy will generate further research; discovery of more microdeletions and other important classes of variants may follow. Detection of such genetic abnormalities in patients being evaluated for surgical treatment might raise concern that a genetic defect, possibly widely expressed in the brain, will affect surgical outcome. METHODS: A reevaluation was undertaken of clinical presurgical data, histopathology of surgical specimen, and postsurgical outcome in patients with mesial temporal lobe epilepsy (MTLE) who have had surgical treatment for their drug-resistant seizures, and who have been found to have particular genomic microdeletions. KEY FINDINGS: Three thousand eight hundred twelve patients with epilepsy were genotyped and had a genome-wide screen to identify copy number variation. Ten patients with MTLE, who had resective epilepsy surgery, were found to have 16p13.11 microdeletions or other microdeletions >1 Mb. On histopathology, eight had classical hippocampal sclerosis (HS), one had nonspecific findings, and one had a hamartoma. Median postsurgical follow-up time was 48 months (range 10-156 months). All patients with HS were seizure-free after surgery, International League Against Epilepsy (ILAE) outcome class 1, at last follow-up; the patient with nonspecific pathology had recurrence of infrequent seizures after 7 years of seizure freedom. The patient with a hamartoma never became seizure-free. SIGNIFICANCE: Large microdeletions can be found in patients with "typical" MTLE. In this small series, patients with MTLE who meet criteria for resective surgery and harbor large microdeletions, at least those we have detected, can have a good postsurgical outcome. Our findings add to the spectrum of causal heterogeneity of MTLE + HS.